With a Mentored Clinical Scientist Development Award the applicant proposes to build upon his initial experience in vascular molecular biology studying the structure and function of the thrombin receptor in the laboratory of Dr. Shaun Coughlin (UCSF). The present proposal, focusing on the signals responsible for monocyte recruitment to the vessel wall, includes a carefully designed program of didactic study and scientific investigation in the laboratory of Dr. Anthony Rosenzweig in the Cardiovascular Research Center (CVRC) of the Massachusetts General Hospital. The rich intellectual environment of the CVRC, under the direction of Dr. Mark Fishman, will optimally foster the candidate's scientific development towards independent investigation. The proposed research project is based on the hypothesis that local expression of adhesion molecules and chemokines plays an important role in mononuclear leukocyte recruitment and the subsequent development of atherosclerotic lesions. Important questions concerning these signals remain: Do chemokines such as monocyte chemoattractant protein-1 (MCP-1) help determine the specificity of leukocyte adhesion to vascular cell adhesion molecule-1 (VCAM-1) by enhancing the binding of specific subpopulations? Does a chemokine gradient play an important role in these effects? Are cell-associated chemokines more potent? To develop vascular models to address these issues, cDNAs for VCAM-1 and wild-type or modified (secreted vs. tethered) chemokines will be substituted for E1 into human Adenovirus type 5 (Ad5) genome to provide efficient, high-level gene transfer to endothelial cells. Preliminary work has already shown that adenoviral transduction perturbs endothelial biology very little in vitro, and the transduction of human endothelial cells (HEC) to express functional VCAM-1 has been completed. In the first phase of the proposed project, the above questions will be addressed in vitro studying the adhesion of specific leukocyte subsets in static assays, under rotation, and in a parallel-plate laminar flow chamber. In a second phase, the same adenoviral constructs will be used in vivo to transduce rabbit carotid artery segments. These studies will determine whether local over-expression of VCAM-1 alone or in combination with chemokine constructs can promote recruitment of leukocytes to the vessel wall, and whether this can modulate the formation of atherosclerotic lesions either in normo- or hypercholesterolemic rabbits.